'NCIS' Cast Tease 'Intense' Season 21 Finale: 'There Are Some Fundamental Changes' (Exclusive)

The cast members spoke with ET from the CBS fall schedule announcement celebration.

NCIS season 21 is going out with a bang!

After hitting 1000 episodes in the franchise earlier this year, the cast members from the mothership show say the upcoming finale is not one to be missed as there could be some big shake-ups for longtime NCIS fans. Talking with ET's Kevin Frazier from the CBS Fall Schedule Celebration on Thursday, six of the show's main stars teased what they could -- which is very little -- about what to expect from the "intense" finale. 

"I'll say this, the finale is not to be missed. There is some intense stuff, and when I say intense, I mean intense, like it's stuff that we haven't hit in a long, long time as far as the life and death that is happening within this episode," said Brian Dietzen, who has played Dr. Jimmy Palmer since the show's debut in 2003. 

"Unbelievable that you revealed nothing and said so much," responded Alden Park actor Gary Cole

Their co-star, Katrina Law -- who joined the show as Jessica Knight in season 18 -- added in her two cents, saying not only will the May 6 finale be one that leaves fans on the edge of their seats, but it will "lead to an interesting next season."

Rocky Carroll, Diona Reasonover, Sean Murray, Katrina Law, Brian Dietzen and Gary Cole from 'NCIS' attend the CBS New Fall Schedule Celebration - Getty Images

"I will say that there is -- there is a lot of soul-searching that goes on during this episode. It's one of my favorite episodes that I read all season, actually the entire time that I've been on NCIS," Law, 38, said. "There's some fundamental changes that are gonna happen to our characters."

According to an episode description, season 21's tenth and final episode will feature Law's character receiving a unique opportunity from NCIS Director Leon Vance, played by Rocky Carroll. The 60-year-old actor also spoke with ET on Thursday and shared that the episode is distinctly special for his character, who first appeared in season 5. 

"Without giving away the form, especially tonight, [my character] had to come to terms with some very personal and also some very professional decisions that could be very life-changing," said Carroll. "All those things could come to a head in the season finale."

The actor -- still remaining mostly tight-lipped about the future of his character and the finale -- opened up about one scene from episode seven, "A Thousand Yards," in which he filmed at a graveyard and worried about his character's safety, as well as his own job security. 

"We shot an episode where my character is standing in the cemetery and I flipped ahead in the script to make sure he leaves the cemetery," he said of the writers keeping him on his toes after 16 seasons. "That's kind of what you do after so many years on the show."

Rocky Carroll in 'NCIS' season 21, episode 7 - CBS via Getty Images

While it may not be Carroll's character at death's door this time around, Sean Murray -- who has dutifully played Agent Timothy McGee since season 1 -- said that since NCIS has been known to kill off a character or two in the past, everyone is on the line. 

"We got some agents in trouble," added Murray, 46. "We got no problem killing people."

"Not me though, I'm too cute to kill," joked Diona Reasonover, who plays Kasie Hines. "I hope so. I think I read the script."

Brian Dietzen as Jimmy Palmer, Gary Cole as Alden Parker, Katrina Law as Jessica Knight, and Wilmer Valderrama as Nicholas "Nick" Torres - CBS via Getty Images

The interview comes on the heels of NCIS: Hawai'i's cancellation after three seasons on air. Late last week, ET confirmed the show's end as sources told Deadline that the forthcoming finale was not written or intended to be the end of the show and will allude to potential season 4 stories. 

Among the most shocked by the cancellation was the show's cast members, including star Vanessa Lachey who shared her heartbreak in a series of Instagram Stories immediately following the news. 

"Gutted, confused, blindsided," the 43-year-old Love Is Blind co-host wrote at the time. 

Lachey -- who just recently appeared in the special 1000th episode alongside cast members from other NCIS shows -- later showed off how her 9-year-old daughter, Brooklyn, tried to cheer her up after the cancellation. 

"Trying to explain the news to my daughter ... and she makes me Mickey ears so I can 'smile' 😩," Lachey wrote. "This decision was bigger than a TV show."